As to the electronic equipment powered by a battery, after replacing the battery many times, a pole patch of the battery becomes black, which results in an unreliable power supply of the electronic equipment. The main reason is that the discharge current of the battery is not reasonably controlled. For example, when replacing the battery for the electronic equipment, a large pulse current occurs at the moment of contacting the battery pole patch with a battery holder of the electronic equipment, and there is spark generation at the contact point of the battery pole patch, and the battery pole patch is oxidized by high-temperature, thereby the pole patch of the battery turns black. In the handhold electronic equipment applied in some flammable and explosive environment, for sake of safety, the discharge energy of the battery needs to be restricted within a certain safety value. The large transient discharge current of the battery brings a lot of potential safety hazard to the storage and usage of the battery. Thereby, how to reasonably restrict the battery discharge current within the safety limiting value without affecting its normal usage is an important technical problem to be solved for battery protection.
At present, the overcurrent protection circuit for battery discharge mainly adopts the following manner: when the battery is in an idle state, a discharge switch transistor is normally switched on; during the battery discharging, when the protection circuit detects that the discharge current of the battery exceeds a designed limiting value, the discharge switch transistor will be switched off after a certain delay time, and the battery discharge is ended; during the switch-off delay time, the discharge switch transistor is continuously switched on, and there is large pulse current through the discharge circuit. The deficiency of this method is that the usage safety of the battery conflicts with the requirement to the delay time by the charge of capacitive load. If the delay time is designed to be relatively short, the switch-off delay time is required to be relatively long when supplying power to the load containing a large capacitor; and if the delay time is not long enough, before the capacitor of the load is fully charged, the battery protection circuit generates a current limiting protection and terminates the discharge, then the load cannot be powered normally. If the delay time is designed to be relatively long, the charge requirement of the load having a large capacitance is satisfied, but if the discharge port of the battery is short-circuited suddenly, a large pulse current will be generated, and there may be a hidden danger of accidents such as fire or burns. Using such battery, the pole patch of the battery of the equipment is usually oxidized and turns black, and then a poor contact occurs.